Collectors It increases the non-wettability of ore particles by water , e . g ., pine oils , xanthates and fatty acids .
Electromagnetic Separation
This method of concentration is employed when either the ore or the lmpurities associated with it are magnetic in nature . e . g ., chromite ,
FeCr2O4 , containing magnetic SiliCIOUS gangue and wolframite FeWO4 , Containing cassiterite , 8nO4 ( non-magnetic impurities ) can be separated by this method .
Electrostatic Separation
This method is used for the separation of lead sulphide ( good conductor ) which is charged immediately in an electrostatic field and is thrown away from the roller from zinc sulphide ( poor conductor ) which is not charged and hence , drops vertically from the roller .
Chemical Method-Leaching
Leaching is the process in which the ore is concentrated by chemical reaction with a suitable reagent which dissolves the ore but not the impurities , e . g ., bauxite is leached with a hot concentrated solution of NaOH which dissolves aluminium while other oxides ( Fe2O3 , TiO2 , SiO2 ), remain undissolved and noble metals ( Ag and Au ) are leached with a dilute aqueous solution of NaCN or KCN in the presence of air .
Extraction of Crude Metals from Concentrated Ore
The concentrated ore is usually converted to oxide before reduction , as oxides are easier to reduce . Thus , isolation of crude metal from concentrated ore involves two major steps :